1. Field of Invention
The present invention relates to a method for forming a material layer. More particularly, the present invention relates to a method for forming a material layer with an anti-reflective surface.
2. Description of Related Art
During a photolithography process of an integrated circuit (IC) fabrication, photo masks are often used to transfer several patterns onto a wafer. During the pattern transferring process, a photoresist layer is irradiated with light passing through the photo mask. After the development process, the unwanted areas of photoresist layer are removed to leave behind the desired patterned photoresist layer. However, it is well known that the photoresist layer is formed over many reflective material layers which often reflect light into regions of photoresist layer that are not intended to be irradiated. The unintentional irradiation causes the resulting patterned photoresist layer to be inaccurate by causing reflective notching in the patterned photoresist layer or inaccurate line width.
Reflective notching on highly reflective substrates and line width (or critical dimension, CD) variations due to topography and film thickness non-uniformity have been a difficult problem for semiconductor manufacturers. A useful method such as an anti-reflective coating (ARC) has been developed to suppress reflectivity, which method involves applying an ARC layer over the reflective material layer before the application of the photoresist layer. However, physical properties including refractive index and the absorption coefficient of the conventional anti-reflective coating cannot be customized to meet different application requirements. That is, it is not easy to adjust the physical property of the currently used anti-reflective coating to obtain the optimized process result.